Foreign Policy Similarity Score
Also known as: Foreign Policy Similarity Measurement, UN Voting Affinity Score, Ideal Point Distance, State Preference Similarity
A foreign-policy similarity score measures how alike two states' revealed foreign-policy positions are — most commonly from their votes in the UN General Assembly, but also from alliance portfolios or treaty positions. It is a workhorse measure of shared interests, affinity, and alignment in dyadic IR. Häge (2011) shows that naive agreement and the popular S-score can be inflated by chance agreement that arises because states differ in how often they take each position, and proposes chance-corrected indices (Scott's π, Cohen's κ) that better isolate genuine alignment.
Key highlights
- Quantifies shared interests and alignment from observable, comparable behavior.
- UN voting provides near-universal, long-running coverage of state positions.
- Chance-corrected indices separate genuine alignment from coincidental agreement.
- Flexible across data sources — votes, alliances, treaties — within one measurement logic.
Intuition
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How it works
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When to use it
Use foreign-policy similarity scores when you need a dyadic measure of shared interests or alignment from revealed behavior — UN voting affinity is the standard. They are central to studies of alliances, aid, conflict, and bloc formation. Prefer chance-corrected indices when states' baseline voting propensities differ and you want genuine alignment rather than coincidental agreement. They are less appropriate when revealed positions poorly reflect the interests of interest, when the issue set is unrepresentative, or when an ideal-point model (which scales positions on a latent dimension) better fits the goal.
Strengths & limitations
- Quantifies shared interests and alignment from observable, comparable behavior.
- UN voting provides near-universal, long-running coverage of state positions.
- Chance-corrected indices separate genuine alignment from coincidental agreement.
- Flexible across data sources — votes, alliances, treaties — within one measurement logic.
- Revealed positions (e.g., UN votes) are partly symbolic and may not reflect material priorities.
- Different measures (raw agreement, S, π, κ, ideal-point distance) can give divergent results.
- Lopsided or strategic voting agendas distort agreement-based scores.
- Cross-time comparability is complicated by changing issue agendas and membership.
Common pitfalls
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Applications
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Frequently asked
Why correct for chance agreement?
Because some agreement between two states arises mechanically from their individual voting tendencies, not from shared interests. If most states vote 'yes' on most resolutions, any two will agree frequently regardless of alignment. Chance-corrected indices like Scott's π and Cohen's κ subtract this expected agreement, so the score reflects how much the states agree beyond chance — capturing choice rather than circumstance, in Häge's terms.
How does this relate to UN voting ideal points?
Agreement-based similarity scores compare positions pairwise, while ideal-point models place each state on a latent foreign-policy dimension estimated from the full voting matrix, so distance in that space measures dissimilarity. Ideal points (e.g., Bailey, Strezhnev, and Voeten) handle changing agendas and provide a dynamic, comparable scale, whereas agreement scores are simpler and directly dyadic. They are complementary measures of alignment with different assumptions.
Is foreign-policy similarity the same as alliance portfolio similarity?
Alliance portfolio similarity is one specific instance, computed from states' alliance commitments. Foreign-policy similarity is the broader concept, most often operationalized from UN voting but applicable to any revealed positions. They share measurement machinery (e.g., the S-score) but draw on different behavior; voting-based scores cover more states and issues, while alliance-based scores focus on security alignment.
Sources
- 1.Häge, F. M. (2011). Choice or circumstance? Adjusting measures of foreign policy similarity for chance agreement. Political Analysis, 19(3), 287–305.
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Cite this page
ScholarGate. (2026, June 22). Foreign Policy Similarity Score. ScholarGate. https://scholargate.app/international-relations/foreign-policy-similarity-score